Thread cutting attachment for a sewing machine

ABSTRACT

The invention comprises a thread cutter for a sewing machine. The cutter comprises a block of material having a plurality of sides, each side providing a different cutting edge. This permits the cutter to be moved to another edge when the first edge becomes dull. In accordance with the present invention the block of material is mounted in a weighted holder which is in turn mounted at the end of a piston rod slidable in and out of an air cylinder. A backing plate is provided against which the cutter is forced by the air cylinder with a sudden burst of air. The optimum angle at which the particular cutting edge meets the backing plate is an angle of 19*. At this angle the cutter operates virtually without a miss. Experiment has indicated that the cutter will operate at a variance of plus or minus four degrees with reasonable efficiency. The cutter is operated by a conventional type of tripping circuit in which a piece of cloth entering the machine trips a sensing device which causes the cutter to operate in front of and at the rear of the cloth to trim the threads.

United States Patent Dunne et al.

[ 51 Oct. 10,1972

1541 THREAD CUTTING ATTACHMENT FOR A SEWING MACHINE [72] Inventors: OwenF. Dunne, Tiverton; William E. Hebert, Portsmouth, both of R.I.;

Ronald Souza, North Westport; Ed-

. ward Wargat, Fall River, both of Mass.

[73] Assignee: Zalking Sewing Machine 8:. Supply Co., Fall River, Mass.

[22] Filed: July 24, 1969 211 Appl. No.: 844,451

[52] US. Cl ..112/252 [51] Int. Cl. ..D05b 65/00 [58] Field of Search..112/252, 122, 129, 130; 83/697, 662, 694; 30/329, 334, 354, 169, 275

[56] References Cited UNITED STATES PATENTS 2,593,144 4/1952 l-lercik..83/694 3,094,031 6/1963 Reeber et a1 ..112/252 X 3,250,237 5/1966Myska. ..112/252 1,663,092 3/1928 Parys ..83/694 2,213,071 8/1940 Keller..30/169 3,430,592 3/1969 Florczak ..112/252 Primary Examiner-James R.Boler Attorney-Cushman, Darby & Cushman ABSTRACT The invention comprisesa thread cutter for a sewing machine. The cutter comprises a block ofmaterial having a plurality of sides, each side providing a differentcutting edge. This permits the cutter to be moved to another edge whenthe first edge becomes dull. In accordance with the present inventionthe block of material is mounted in a weighted holder which is in turnmounted at the end of a piston rod slidable in and out of an aircylinder. A backing plate is provided against which the cutter is forcedby the air cylinder with a sudden burst of air. The optimum angle atwhich the particular cutting edge meets the backing plate is an angle of19. At this angle the cutter operates virtually without a miss.Experiment has indicated that the cutter will operate at a variance ofplus or minus four degrees with reasonable efficiency. The cutter isoperated by a conventional type of tripping circuit in which a piece ofcloth entering the machine trips a sensing device which causes thecutter to operate in front of and at the rear of the cloth to trim thethreads.

2 Claims, 6 Drawing Figures PKTENTED "B 10 I973 3.6 96 7 TO SHEET 1 OF 2COMPRESSED AIR PRESSURE AIR FILTER REeu ATOR -fi 2 42 40 4/ PISTON 0 OTENQI'ITROA-AIIEE L H SENSOR SENSOR AMPLIFIER VARIABLE 44 TIME DELAY MAKE45 SOMS ELEgRI'RIC SEIIDECAI'ER PULSE SOLENOID PISTON3 vALvE 47 CLOTHExIT VARIABLE TIME DELAY MAKE INVENTORS OWEN F. DUNNE WILLIAM E. HEBERTESI'IIQRB vr F I G. 6 BY ATTORNEYS THREAD CUTTING ATTACHMENT FOR ASEWING MACHINE Our present invention relates to sewing machines and moreparticularly to a novel construction of a cutter attachment for a sewingmachine.

The principal object of the present invention is to provide a cuttingattachment for trimming threads hanging from work passing through thesewing machine both in front of and at the rear of the work.

Another object of the present invention is to provide a cutter whichwill operate witha maximum efficiency and practically no misses.

A further object of the present invention is to provide a cuttingattachment in which the cutting element has a long life.

Another object of the present invention is to provide a cuttingattachment in which the cutting element is provided with a plurality ofcutting edges which are interchangeable as each wears out.

A further object of the present invention is to provide a cuttingattachment for cutting thread on a sewing machine which is simple inconstruction and easy and economical to manufacture and assemble.

With the above and other objects and advantageous features in view ourinvention consists of a novel arrangement of parts more fully disclosedin the detailed description following in conjunction with theaccompanying drawings and more particularly defined in the appendedclaims.

In the drawings,

FIG. 1 is a perspective view of a cutting attachment of the presentinvention mounted on a sewing machine head.

FIG. 2 is a side elevation thereof.

FIG. 3 is a view similar to FIG. 1 showing an alternate mounting of thedevice.

FIG. 4 is a side elevation of the mounting shown in FIG. 3.

,FIG. 5 is an exploded perspective view of the cutting element and itsholder.

FIG. 6 is a block diagram of the hookup for operating the cutter of thepresent invention.

It has become desirable to provide certain types of sewing machines withthread cutting attachments. Certain machines, such as lock-stitchmachines, over-lock machines, etc. use a considerable amount of thread.When the operator, frequently on piece work, feeds successive pieces ofcloth through the machine the operator normally allows the thread to runbetween pieces so that the pieces of cloth are connected by chains ofstitches which must be cut by hand. Accordingly cutting devices havebeen provided which automatically trim the cloth as it passes throughthe needle. A sensing device is provided of various forms which istripped by the cloth. The cutter then cuts the thread in front of thecloth and at the rear of the cloth to provide a complete trimmingaction. Various types of cutters have been provided for this purpose.Scissor type cutters have been popular and are the only ones that can beused in certain applications. The present invention is directed towardsa chopping or guillotine type cutter.

Referring more in detail to the drawings illustrating our inventionFIGS. 1, 2 and 5, show the chopping type cutter mounted on a sewingmachine. Since the machines may vary in the type and manufacture, the

machine 10 illustrated in FIGS. 1 and 2 is merely representative of anytype of sewing machine. Mounted at the end of the machine 10 is aholding plate 11 on which is mounted an elongated bracket 12 whichextends forwardly of the machine 10 at a slight downward angle. Thebracket 12 is provided with an integral supporting slip 13 extendinghorizontally at right angles to the bracket as shown in FIG. 1. Notethat in view of the downward angle of the bracket 12, the surface of thesupporting strip 13 is also at an angle from the horizontal. Mounted onthe supporting strip 13 is an air cylinder 14 of conventional type fromwhich the piston rod 15 extends downwardly.

The cutter comprises a block 16 illustrated as a square block with eightseparate and distinct cutting edges 17. The block is shown forillustrative purposes but other blocks with more or less cutting edgesmay also be used. The block 16 is mounted in a holder 18 of comparativethickness and weight in the form of a rectangular block taperingdownwardly at 19 to a central axial slot 20 into which the cutter 16fits snugly. A pair of set screws 21 enters transversely into thetapered portions 19 from each side to lock the cutter l6 firmly inplace. The holder 18 is provided with a threaded opening 22 in the upperend for mounting on the piston rod 15 as shown in FIGS. 1 and 2.

The sewing machine 10 is provided with the plate 23 on which the presserfoot 24 is operable in the conventional manner. Mounted behind theplate23 we now provide a generally rectangular plate 25 having arectangular cutout portion 26 from the rear edge inwardly and positionedslightly to one side. The large part of the plate, to the right in FIG.1, is provided with the mounting screws 27 for locking the plate 25 tothe machine. The rear edge of the cutout portion 26 is pro vided with atapered portion 28 providing a flat surface extending downwardly fromthe top edge of the plate 25 towards the bottom. The cut thread isnormally picked off at this point'by any desired device, andconventionally, by a suction device.

As can be seen in FIGS. 1 and 2, downward movement of the piston rod 15will force the cutter 16 against the plate 25 so that the bottom edge ofthe cutter hits the top of the plate at an angle 29. For best resultsthis angle should be 19. Applicants have found that at an angle of 19the cutting action will be virtually without error. However, the devicewill operate efficiently within a range of plus or minus four degrees.It should be noted that in the operation of the device, compressed airis lead into the cylinder 14, suddenly and the result is that the pistonrod 15 will slam the cutter 16 against the plate 25 with great force.Since the cutting distance or movement of the cutter is comparativelysmall the bulk of the holder 18, with the weight provided thereby, addsconsiderably to the efficiency of the cutter.

In some installations, it becomes impossible to mount the cutter closeenough to the machine, in the manner shown in FIGS. 1 and 2, to keep thecutter at an angle of l9. In such cases the cutter can be mounted asshown in FIGS. 3 and 4. In this form the sewing machine 30 is againprovided with the end plate 31 and the bracket 32 is identical to thebracket 12 in FIG. 1. However it should be noted that the bracket 32 isnow mounted at a sharp downward angle which extends the cylinder 33 andpiston rod 34 at a much greater angle. However at this'angle' the pistonrod can move the holder 35 and its accompanying cutter 35 into the samespot under the sewing machine head. This is essential since the cuttingaction must take place as close to the presser foot as possible.However, in this form the plate 37 is mounted so that the cutting head36 strikes the tapered surface 38 instead .of the top flat portion ofthe plate. By tapering the surface 38 at the proper angle, the anglebetween the cutting edge of the cutter 36 and thetapered portion38 willbe l9 at 39. Thus, in this form the cutter strikes the tapered surfacesuch as the surface 28 shown in FIG. 1 instead of the top of the plateto maintain the desired angle of 19 or thereabouts. 1

Operation of this type of cutter is generally provided by the generalhookup shown in block diagram in FIG. 6. A source of compressed air 40is piped through an air filter 41 and pressure regulator 42 to the oiler43 and the electric air solenoid valve 44. It is the operation of thisvalve which allows the compressed air to pass into thecylinder l4 andits associated piston. The solenoid on the other hand is operated by acloth sensor 45 connected to a source of power 46 and through a delayselector 47, which is used to regulate the closeness of the cutter tothe cloth, to the entrance and exit'time delay devices 48 and the finalpulse 49 to operate the solenoid valve 44.

Since cutters have been used on sewing machines, various circuitshave-been provided for sensing and operating a cutting device. Thedevice illustrated in FlG.6 is merely illustrative and any type ofcircuit may be providedThe device of the present invention thereforeprovides a guillotine type cutter in which the cutting element isprovided with a multiplicity of edges. As one of the cutting edgesbecome dull, it is merely necessary to loosen the set screws 21 and turnthe cutter .to a new edge. Furthermore, applicants have found that theweighted holder 18 and the angle of 19 provides avmost efficient cutterwith practically no misses. The mounting on a sewing machine with thetapered portion of the plate permits the maintenance of the 19 angle indifferent types of machines. Furthermore, applicantshave found that theangle of 19 and the type of cutter illustrated herein have one othergreat advantage. As the cutter is used a small burr is advantages of thepresent invention will be readily apparent to a person skilled in theart.

We claim:

1. A cutting attachment in combination with a sewing machine comprisinga sewing machine having a head and a workplate, a supporting platemounted at the end of said sewing machine head, a supporting bracketmounted on said plate and extending rear wardly of said head an aircylinder mounted on said bracket, a piston rod extending downwardly fromsaid cylinder, a thread cutter having a cutting surface, means mountingsaid thread cutter at the end of said piston rod, a base plate mountedon the sewing machine adjacent the back edge of said sewing machineworkplate having a rectangular cut out portion, the back edge of saidcut out having a tapered surface, said cutter striking said taperedsurface at an angle of 19 between said tapered surface and said cuttingsurface of said thread cutter, and means for activating said cylinderand piston rod to strike said cutter against said base plate on movementof a piece of work through said sewing machine.

2. A cutting attachment as in claim 1, wherein said cutter comprises ablock having a plurality of cutting edges.

1. A cutting attachment in combination with a sewing machine comprisinga sewing machine having a head and a workplate, a supporting platemounted at the end of said sewing machine head, a supporting bracketmounted on said plate and extending rearwardly of said head, an aircylinder mounted on said bracket, a piston rod extending downwardly fromsaid cylinder, a thread cutter having a cutting surface, means mountingsaid thread cutter at the end of said piston rod, a base plate mountedon the sewing machinE adjacent the back edge of said sewing machineworkplate having a rectangular cut out portion, the back edge of saidcut out having a tapered surface, said cutter striking said taperedsurface at an angle of 19* between said tapered surface and said cuttingsurface of said thread cutter, and means for activating said cylinderand piston rod to strike said cutter against said base plate on movementof a piece of work through said sewing machine.
 2. A cutting attachmentas in claim 1, wherein said cutter comprises a block having a pluralityof cutting edges.